---
title: "Use Flux 2 in OpenClaw via RunAPI — Image API Guide"
url: "https://runapi.ai/openclaw-flux-2.md"
canonical: "https://runapi.ai/openclaw-flux-2"
locale: "en"
model: "flux-2"
---

# Use Flux 2 in OpenClaw.

Flux 2 by Black Forest Labs offers two quality tiers — Pro for fast, affordable generation at 5 cents per image, and Flex for higher-fidelity output. Both support text-to-image and multi-source remix at 1k or 2k resolution. OpenClaw agents call it through the same RunAPI key used for chat.

## API example

```bash
curl -X POST https://runapi.ai/v1/text_to_image \
  -H "Authorization: Bearer $RUNAPI_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "flux-2-pro-text-to-image",
    "prompt": "a ceramic vase with dried flowers on a linen tablecloth, natural window light, 35mm film grain",
    "aspect_ratio": "3:4",
    "output_resolution": "2k"
  }'

```

### Response

```json
{
  "task_id": "tsk_abc123",
  "status": "pending",
  "model": "flux-2-pro-text-to-image"
}

```

## How it works

1. **Configure RunAPI** — Set the RUNAPI_API_KEY environment variable. If you already configured RunAPI as an OpenClaw provider for chat, the same key works for Flux 2 image generation — no extra setup needed.
2. **Call Flux 2** — Send a POST request to the text_to_image endpoint with model set to flux-2-pro-text-to-image. Include a prompt, and optionally set aspect_ratio (1:1, 4:3, 16:9, etc.) and output_resolution (1k or 2k). For multi-source remixing, use the remix_image endpoint with source_image_urls instead.
3. **Get the result** — The endpoint returns a task ID. Poll the task status endpoint until the status changes to completed, then retrieve the generated image URL from the response. RunAPI SDKs and the CLI handle polling automatically.

## Parameters

| Parameter | Type | Description |
|-----------|------|-------------|
| `model` | `string` | Required. flux-2-pro-text-to-image, flux-2-flex-text-to-image, flux-2-pro-remix-image, or flux-2-flex-remix-image. |
| `prompt` | `string` | Text description of the image to generate. |
| `aspect_ratio` | `string` | Optional. Output aspect ratio: 1:1, 4:3, 3:4, 16:9, 9:16, 3:2, or 2:3. Remix endpoints also accept auto. |
| `output_resolution` | `string` | Optional. 1k (default) or 2k. Higher resolution costs more per image. |
| `source_image_urls` | `array` | Required for remix_image. Array of source image URLs to blend or transform. |
| `callback_url` | `string` | Optional. Webhook URL for async completion notification. |

## FAQ

### What is the difference between Flux 2 Pro and Flux 2 Flex?

Pro is the faster, more affordable tier at 5 cents per 1k image. Flex produces higher-fidelity output at 14 cents per 1k image. Both share the same API parameters and support text_to_image and remix_image endpoints.

### How does Flux 2 compare to Midjourney for photorealistic images?

Users report Flux 2 matches or beats Midjourney on photorealism and material fidelity, with the advantage that it runs through a standard API endpoint rather than a Discord bot. It has caught up on text rendering too, though Ideogram V3 still leads on small-point typography.

### Does Flux 2 output resolution affect pricing?

Yes. Each variant bills per image with resolution-based pricing. For example, Flux 2 Pro costs 5 cents at 1k and 7 cents at 2k. Flux 2 Flex costs 14 cents at 1k and 24 cents at 2k. Check the RunAPI pricing page for current rates.

### How does Flux 2 compare to Flux Kontext?

Flux Kontext specializes in text-guided editing and character consistency with a single input image. Flux 2 focuses on text-to-image generation and multi-source remixing with Pro/Flex quality tiers and selectable output resolution. Both are by Black Forest Labs and available through the same RunAPI key.

### Is Flux 2 async or sync?

Async. The API returns a task ID immediately. Poll the task status endpoint or set a callback_url webhook to receive the completed image URL. RunAPI SDKs and the CLI handle polling automatically.


## Links

- [OpenClaw setup guide →](https://runapi.ai/openclaw)
- [Flux 2 models →](https://runapi.ai/models/flux-2)
- [Model catalog](https://runapi.ai/models)
- [API docs](https://runapi.ai/docs)